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Biomedical subjects

B M Moores

Publications and source records attributed to B M Moores.

At least 37 records · Page 2Linked to original sources
PubMed1984

Noise and contrast detection in computed tomography images.

A discrete representation of the reconstruction process is used in an analysis of noise in computed tomography (CT) images. This model is consistent with the method of data collection in actual machines. An expression is derived which predicts the variance on the measured linear attenuation coefficient of a single pixel in an image. The dependence of the variance on various CT scanner design parameters such as pixel size, slice width, scan time, number of detectors, etc., is then described. The variation of noise with sampling area is theoretically explained. These predictions are in good agreement with a set of experimental measurements made on a range of CT scanners. The equivalent sampling aperture of the CT process is determined and the effect of the reconstruction filter on the variance of the linear attenuation coefficient is also noted, in particular, the choice and its consequences for reconstructed images and noise behaviour. The theory has been extended to include contrast detail behaviour, and these predictions compare favourably with experimental measurements. The theory predicts that image smoothing will have little effect on the contrast-detail detectability behaviour of reconstructed images.

Humans↗
PubMed1982

An assessment of the radiation dose received by staff using fluoroscopic equipment.

Measurements of scattered radiation were made on two fluoroscopic installations, one with an overcouch tube and one with an undercouch tube. The annual doses to staff involved in a fluoroscopic procedure undertaken on both types of unit were estimated using measured dose rates and weighting factors referred to in ICRP 26. Environmental monitoring at the protective barrier was performed for various room layouts to determine the effect of both equipment and room design on the annual dose received by staff at the control panel. In all circumstances the annual dose to staff inside the control cubicle was negligible.

Environmental Exposure↗
PubMed1981

A suggested theory of the conventional tomographic imaging process.

An attempt is made to re-examine the well established theoretical basis of conventional tomography in the light of more detailed techniques being applied elsewhere in image analysis. Transfer function theory has been used to quantify the amount of edge detail reproduced by this process and the information in a tomogram is investigated in terms of edge detail associated with well resolved (unblurred) detail and also that associated with particular anatomical layers within the tomographed object, the theory has been used to define a cut plane thickness. A variety of different tube movements have been considered and calculated values of cut plane thickness are compared with those predicted by a simple geometric model. Besides the blurring associated with the tube movement the effect of x-ray focal spot, film-screen combination and also visual response of the observer have been included and their importance in the definition of cut plane thickness highlighted. One advantage of this approach appears to be the facility to quantify the performance of different tomographic tube movements and highlight the role of tomographic detail reproduced from body sections well removed from the cut plane.

Humans↗
PubMed1980

An atmospheric pressure ionography system suitable for mammography.

Ionography is a possible replacement for silver halide based imaging systems in diagnostic radiology. This type of imaging depends upon the ionisation produced in a gas by incident x-radiation. The ions formed are collected on a plastic foil and the image is made visible by a suitable development process. The physical design properties which can affect sensitivity and image quality of an ionography system are outlined in this paper. Based upon the requirements of adequate sensitivity and resolution an atmospheric pressure ionography system is described which has been designed primarily for use in mammography. Freon 13B1 gas was chosen as the x-ray absorbing medium because it contains a relatively high atomic number atom (bromine, Z = 35) and also has a high density. It is a relatively cheap gas, has a high breakdown potential and has satisfactory resolving capability, particularly when employed at atmospheric pressure with low energy x-ray beams. The performance of the system is discussed in terms of sensitivity and resolution. Problems associated with an atmospheric pressure system are outlined and possible solutions described. Preliminary clinical results obtained with the system are also presented.

Atmospheric Pressure↗
PubMed1979

Light output and x-ray attenuation measurements at mammographic beam qualities for nine commercial intensifying screens.

X-ray attenuation and intensity of light emitted were measured for nine intensifying screens used in mammography. Incident beam qualities with half value layers in the range of 0.38 to 2.68 mm Al were used to simulate the range of clinical conditions encountered in mammography. All the screens attenuated the x-ray beam to a similar extent at these beam qualities, but a wide variation in the intensity of light emitted was observed. The interrelation of the measured physical parameters in determining both the system speed and noise properties is discussed.

Female↗
PubMed1979

A quantitative evaluation of film and film/screen combinations for mammographic examination.

A test phantom containing simulated micro-calcifications was constructed. This was imaged by seven systems suitable for use in mammography, firstly in scatter-free conditions and secondly with the addition of tissue-equivalent scattering material. The ability of the systems to resolve micro-particles of known size was assessed using the techniques of signal detection theory. The resultant receiver operating characteristic curves separated the systems into three major groups. Firstly, high resolution systems requiring high radiation dose techniques; secondly at the other extreme, a mediocre imaging system producing its results at low radiation levels; and thirdly a larger middle group producing intermediate resolution of fine particles at similar, acceptable dose levels. The ability to image small particles does not increase linearly with the radiation dose. Scatter did not affect all of the systems to the same extent.

Data Display↗
PubMed1978

Light output and X-ray attenuation measurements for some commercial intensifying screens.

The spectral content and intensity of light emission together with the x-ray attenuation have been measured for a selection of commercially available intensifying screens used in diagnostic radiology. Incident x-ray beam qualities with half value layers between 3.8 to 10 mm AI were employed in order to simulate a wide range of clinical situations. The measurements of spectral content demonstrate the wide variations in spectral emission which now exist between screens employing different phosphor materials. Similarly, a wide variation in the intensity of light emission is observed for screens employing different phosphor materials and also for screens employing the same material. The interrelation of the measured physical properties affects both the system speed and noise properties and needs to be considered when comparing the performance of different systems.

Radiographic Image Enhancement↗
PubMed1977

Eye dose measurements using conventional and rare-earth screens during tomography of the para-nasal sinuses.

Eye dose measurements have been performed when using medium speed conventional and rare-earth screen-film combinations during tomography of the para-nasal sinuses. The measurements show that using conventional intensifying screens with the A.P. view a total eye dose of about 20 rad may be given during an examination. This eye dose can be reduced by 98% using the P.A. position. If rare-earth screen/film combinations are employed the eye dose measured in the A.P. view was reduced by 75% of that obtained with conventional screens without detectable loss of image quality. A total eye dose reduction of about 99.5% was measured in the P.A. view with the rare-earth systems.

Ear, Middle↗